Apparatus and methods for a vehicle shock absorber

ABSTRACT

A method and apparatus for a vehicle shock absorber comprising a main damper cylinder, a first reservoir and a second reservoir. One embodiment includes a first operational mode where both reservoirs are in fluid communication with the cylinder. In a second operational mode, only one reservoir communicates with the cylinder during fluid evacuation from the cylinder. In each mode, rebound from either or both reservoirs may travel through a single, user-adjustable metering device.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims priority toand benefit of co-pending U.S. patent application Ser. No. 12/794,219,filed Jun. 4, 2010, which claims benefit of U.S. provisional patentapplication Ser. No. 61/184,763, filed Jun. 5, 2009, which is hereinincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a suspensionsystem, more particularly, a shock absorber with multiple reservoirchambers (IFPs), especially one permitting selective communicationbetween the reservoirs and a main damper chamber.

2. Description of the Related Art

Integrated damper/spring vehicle shock absorbers often include a damperbody surrounded by a mechanical spring. The damper consists of a pistonand shaft telescopically mounted in a fluid filled cylinder. The purposeof the damper is to control the speed at which the shock absorberoperates. The mechanical spring provides resistance to shock events andmay be a helically wound spring that surrounds the damper body. Variousintegrated shock absorber configurations are described in U.S. Pat. Nos.5,044,614, 5,803,443, 5,553,836 and 7,293,764; each of which is hereinincorporated in its entirety by reference. A shock absorber of U.S. Pat.No. 7,293,764 is shown herein as FIG. 1. As shown, the shock absorber 10comprises a damper assembly 15 consisting of a chamber 18 housing apiston (not shown) and rod 20 and a helical spring 25 disposed on thedamper in a manner whereby the spring and damper operate together. Theshock absorber is attached via eyeholes 30, 35 to separate portions of avehicle (not shown) and the shock operates when there is relativemovement between those portions.

Various arrangements permit aspects of the shock absorber to be adjustedor changed by an end user. For example, U.S. Pat. No. 5,044,614 (“614patent”) shows a damper body carrying a thread 42. A helical spring 18surrounds the damper body. The compression in the helical spring 18 maybe pre-set by means of a nut 48 and a lock nut 50. The nut 48 may betranslated axially relative to the body (“tube”) 16 and thread 42 byrotating the nut 48 around the threaded sleeve 42. Rotation of the nut48 in a given direction (e.g. clockwise as viewed from end 44 for aright hand thread 42) will cause the nut to move toward the retainerclip 26 thereby compressing spring 18 between the nut 48 and theretainer clip 26. Once the spring 18 is in a desired state ofcompression, lock nut 50 is rotated, using a wrench, up against nut 48and tightened in a binding relation therewith.

Some shock absorbers utilize gas as a spring medium in place of, or inaddition to, mechanical springs. Gas spring type shock absorbers, havingintegral dampers, are described in U.S. Pat. Nos. 6,135,434, 6,360,857and 6,311,962, each of which is herein incorporated in its entirety byreference. U.S. Pat. No. 6,360,857 shows a shock absorber havingselectively adjustable damping characteristics. U.S. Pat. No. 7,163,222,which is incorporated herein in its entirety by reference, describes agas sprung front shock absorber for a bicycle (a “fork”) having aselective “lock out” and adjustable “blow off” function.

The spring mechanism (gas or mechanical) of some shock absorbers isadjustable so that it can be preset to varying initial states ofcompression. In some instances, the shock spring (gas or mechanical) maycomprise different stages having varying spring rates thereby giving theoverall shock absorber a compound spring rate depending varying throughthe stroke length. In that way the shock absorber can be adjusted toaccommodate heavier or lighter carried weight, or greater or lesseranticipated impact loads. In vehicle applications, including motorcycleand bicycle applications and particularly off-road applications, shockabsorbers are pre-adjusted to account for varying terrain andanticipated speeds and jumps. Shocks are also adjusted according tocertain rider preferences (e.g. soft-firm).

A type of integrated spring/damper shock absorber, having a gas spring,is shown in FIG. 28, for example, of U.S. Pat. No. 7,374,028, which isincorporated herein in its entirety by reference. The shock shown inFIG. 28 of the '028 patent also includes an “adjustable intensifierassembly 510.” That intensifier or “reservoir” accepts damping fluidfrom chamber 170 as the fluid is displaced from that chamber by theincursion of rod 620 into chamber 170 during a compression stroke of theshock. The intensifier valve assembly regulates flow of damping fluidinto and out of the reservoir, and an embodiment of the valve assemblyis shown in FIG. 17 of the patent.

In some instances, reservoir portions of dampers are separate componentswhereby a separate chamber is provided for fluid expelled from the mainchamber. A damper with such a remote reservoir is illustrated in FIG. 9of the '028 patent incorporated herein. Other suspension systems usemultiple, separate reservoir-type chambers that divide the usabledampening capability of the shock. In these designs, fluid is pushedfrom the main dampening cylinder and with valving, the reservoirchambers are utilized in various ways. By using one or both chambers,the travel available in the shock can be determined by a user.Configurations of multiple reservoir-type shocks are shown in U.S. Pat.No. 7,219,881, which is incorporated herein in its entirety byreference. The presently available dual reservoir designs havedrawbacks. For example, utilization of both reservoirs is achievedsolely by use of two separate and distinct paths between the mainchamber and each of the reservoirs. Because each path has its ownmetering devices, especially in the rebound direction, there is always apotential of one of the reservoir chambers to lose fluid and “crash”when the metering devices are set differently.

What is needed is a multiple reservoir suspension system that ensuresthat each reservoir retains sufficient operating fluid. What is neededis a multiple reservoir system having simplified controls.

SUMMARY OF THE INVENTION

The present invention generally relates to a vehicle shock absorbercomprising a main damper cylinder, a first reservoir and a secondreservoir (although the principles herein may be extended to a third ormore reservoirs as well). In one embodiment, a first operational modeincludes a fluid path between the cylinder, optionally via a valve, anda first reservoir and then a path between the first and a secondreservoir. In a second operational mode, a fluid path is utilizedbetween the cylinder, optionally via a valve, and one of the reservoirs,the path excluding the other reservoir. Operation between the modes isuser selectable.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features can be understoodin detail, a more particular description may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of the invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a perspective view of a shock absorber including a damper anda spring.

FIG. 2 is a schematic view of a damper with two reservoirs.

FIG. 3 is a section view of a Schrader-type valve.

FIG. 4 is a section view of a Schrader-type valve.

FIG. 5 is a section view of a Schrader-type valve.

FIG. 6 is a section view showing a damper cylinder with a valve adjacentthereto and fluid paths between the damper cylinder and valve.

FIG. 7 is a section view showing a valve and two reservoirs with fluidpaths therebetween in a “full-travel” mode of the shock absorber.

FIG. 8 is a section view showing the valve and two reservoirs with fluidpaths therebetween in a “half-travel” mode.

FIG. 9 is a section view showing a rebound pathway for fluid between theReservoirs.

DETAILED DESCRIPTION

FIG. 2 is a schematic view of a shock absorber embodiment 100 thatutilizes a main damper 125 and two reservoir chambers or InternalFloating Piston chambers (IFPs) 300, 400. Unlike the shock of FIG. 1,the shock embodiment of FIG. 2 operates as a “pull shock”, which meansthe shock absorber gets pulled in tension to an extended condition asthe suspension mechanism driving the shock reacts to compressive forcescaused by terrain irregularities (bumps that compress the rear wheeltoward the bicycle frame). Whether or not a shock absorber extends orcompresses in response to compressive terrain features is a function ofthe suspension linkage in which the shock is mounted. In one embodiment,the oil chamber and gas chambers of the shock are in reversed placementrelative to the main piston and shaft seal end of the main cylinder.With a “push shock”, on the other hand, the shock absorber gets pushedto a shorter condition as the suspension mechanism driving the shockaccommodates compressive terrain irregularities. Other than appearanceand reversed operation, the principles of pull and push shocks remainsubstantially the same and the embodiments described and claimed hereinare equally intended for both.

In one embodiment of the invention, a shock absorber is operativelymounted between an unsprung portion of a bicycle, such as the swing armand rear axle, and a sprung portion of the bicycle such as the frame. Arepresentative example embodiment of shock absorber derives from theshock absorber shown in FIG. 28 of, and elsewhere in, U.S. Pat. No.7,374,028 which is incorporated herein by reference.

In the embodiment of FIG. 2, the main damper 125 has a piston 180mounted on a shaft 185. The piston 180 is solid without the typicalpassages formed therethrough for the passage of fluid from one side ofthe piston 180 to the other side (although in some embodiments thepiston may also included damping passages and valving). The shaft andpiston assembly is fitted into a main cylinder 178. The cylinder isdivided into a fluid (e.g. damping fluid, oil) chamber 188 andcompressible fluid or gas (e.g. air, nitrogen) chamber 189 and thisdivision is created by the solid piston, which seals on its OD with aseal such as an O-ring seal 190. The shaft 185 is also sealed where itextends a bulkhead of the main cylinder 178 with O-ring seal 186. Whenthe shaft is pulled, the air chamber 189 within the cylinder becomesbigger (increases in volume) and the fluid chamber 188 within thecylinder becomes smaller. Fluid is pushed by the piston from the fluidchamber 188, through a compression damping circuit that includes a valve200, and into one or both of the two IFP chambers 300, 400, as will bedescribed herein. The first chamber 300 and second 400 IFP chambers arealso each separated into a fluid chamber 301, 401 and an gas (e.g. air)chamber 302, 402 by a floating piston 305, 405 of each chamber 300, 400.In each case the floating piston is sealed within the chamber by asuitable seal such as an O-ring seal 306, 406. As fluid moves from themain cylinder fluid chamber 188 into the fluid chambers 301, 401, theIFP chambers 301, 401 increase in volume at the expense of the gaschamber 302, 402 volumes (as the gas chambers decrease in volume bymovement of the floating pistons).

In use, gas pressure in the gas chamber 189 of the main cylinder 178 isadjustable using a fill valve 155. Gas pressure in the IFPs 300, 400 isalso user-adjustable. As shown in one embodiment of FIG. 2, the gasvolumes 302, 402 of the IFPs are in fluid communication with a singlefill valve 315 via a communication path 311. In one embodiment, anothervalve 500 adjacent the fill valve 315, or integral therewith, is aSchrader-type valve for filling the first and second IFP air chambers302, 402 to an equal pressure and then subsequently maintainingisolation of chambers 302 and 402 one from the other during use. TheSchrader valve includes an axially movable stem member depressible tocommunicate with the first chamber through a first port and furtherdepressible to communicate with the first and second chambers through asecond port. In this manner, a single volume can be filled orpreferably, both volumes, 302, 402 can be filled to an equal pressure ina single action by the user. Such an arrangement is shown and describedin detail (see FIGS. 11, 12, 13) in Patent Application Publication No.US 2009/0236807 A1, assigned to the owner of the present invention, andthat publication is incorporated herein by reference in its entirety.

In one embodiment utilizing the Schrader-type valve, the first 302 andsecond 402 volumes are filled by introducing pressure, from a suitablegas pump or other source of pressurized gas, into the gas fill valve 315which includes or operates with, or is replaced by, a Schrader-typevalve 500 as shown in FIGS. 3-5. Referring to FIG. 3, the valve 500 isdesigned to fill both of the first and second volumes with pressurizedgas from the single valve body 510. In FIG. 3, the valve is closed withno communication of air therethrough.

In one aspect a valve stem 520 is connected through a valve core 525 toa primary fill valve 530 such that axial movement of the spring loadedvalve stem 520 causes an opening of the primary fill valve 530 and axialmovement of a valve pusher stem 535. Sufficient axial movement of thevalve pusher stem 535 closes a gap 540 until the valve pusher stem 535contacts the second chamber fill valve stem 545. Following such closureof the gap 540, further movement of the valve pusher stem 535 moves thesecond fill valve stem 545 and correspondingly separates the second fillvalve 550 from a valve seat. The design ensures that sufficient axialmovement of the valve stem 520 opens the primary fill valve 530 andfurther movement of the valve stem subsequently opens the second fillvalve 550.

FIG. 4 illustrates a Schrader-type valve 500 with the valve stem 520depressed and primary fill valve 530 open. In this position, pressurizedair communicates through the valve 530 and to exit 560 formed in valvebody 510 which preferably leads to the first gas volume 302. FIG. 5illustrates the Schrader-type valve 500 with valve 530 open and gap 540closed. Further, the second fill valve stem 545 has been axiallydepressed to open secondary fill valve 550. With the components of theSchrader-type valve in the position shown in FIG. 5, the first andsecond volumes 302, 402 can be filled simultaneously. Gap 540 can besized to determine operative characteristics of the valve 500. Forexample, a gap of 0.050″ in one embodiment leaves a gap of sufficientwidth that second chamber is not inadvertently filled along with thefirst chamber.

The valve stem 520 may be moved either mechanically, by a probe on apressure fitting (not shown) of a pressurized gas source, or solely bythe introduction of pressurized gas into the fill valve body 510 whereinthe pressurized gas acts over the surface area (i.e. piston area) of theprimary fill valve 530. In one embodiment, the dimension of the gap 540is set such that movement of the valve stem 520 and primary fill valve530, caused solely by the introduction of pressure, is not sufficientunder normal operating pressures to close the gap 540 between the valvepusher stem 535 and the secondary fill valve stem 545. Correspondingly,only the primary fill valve 530 is opened allowing pressurized gas to beintroduced into the first volume 302. Movement sufficient to close thegap 540 and open secondary fill valve 550 may be induced by a gas fillfitting (not shown) connected to the fill gas pressure source and havinga protrusion or “stinger” in it that is dimensioned to move the valvestem a sufficient distance to close the gap and open the secondary fillvalve 550. Alternatively, a fitting may be used without a stinger andthe valve stem 520 may be moved by gas pressure from the fill gaspressure source. At certain lower velocities (based on lower fill gaspressures or introduction rates) the movement of the valve stem will beinsufficient to open the secondary chamber fill valve and only the firstvolume will be filled. Conversely the respective porting of the valveassembly can be reversed (not shown) so that initial movement of thevalve stem opens the second fill valve and further movement closes thegap and opens the primary fill valve.

Optionally, a mechanical probe, attached to a pressure hose fitting (notshown) for example, is used to move the valve stem 520. The length ofthe probe is sufficient to open the primary fill valve 530, close thegap 540, cause movement of the valve pusher stem 535 and secondary fillvalve stem 545 and thereby open the secondary fill valve 550.Correspondingly, pressurized gas flows into the first volume 302 aspreviously described and also through the open secondary fill valve 350,permitting flow into the second volume 402.

In operation, the IFP gas pressure acts as the shock absorber mainspring in one embodiment tending to resist extension of the “pull”shock, thereby providing a spring function for the shock absorber 100,while the main cylinder air chamber 189 acts as a shock absorber“negative spring” for the “pull” shock, tending to resist compressionthereof and, by user adjustment, aiding in tailoring of gas springcurves by the user. The embodiment of FIG. 2 is designed whereby gaspressure in IFP cylinders 300, 400 will bias the piston 180 towards theclosed end of the main cylinder 178.

In one embodiment valve 200 permits operation of the shock absorber ofFIG. 2 in three different settings: full-travel, half-travel and lockout. The system is intended to be user-operable whereby the operator ofthe vehicle can shift the valve 200 between the three functions. In thefull-travel setting, the oil is pushed by the piston 180 from the maincylinder 178 and along a path that is shown on schematic FIG. 2 as 150.The fluid extends through valve 200 to first IFP 300 and then, via aseparate and direct communication path 160, to IFP 400. This settingmakes both IFP gas chambers (and volumes) 302, 402 available as gassprings in operation of the shock absorber. Further, the fluid istransferred, during both extension and compression of the shock, along apath that includes the damping fluid reservoirs in series. Because ofthat, all of the reservoir damping liquid is available during the fullstroke of the shock absorber on every stroke. Damping fluidcommunication directly between reservoirs ensures that the reservoirsremain relatively equalized (or at a known and predetermined operationaldifferential) during operation and are not subject to unplanned anddetrimental fluid fill fluctuations. Additionally, the sequentialoperation permits any metering of fluid to be performed at a singlelocation so that there is no need (although optionally there may stillbe) to meter the fluid separately in each IFP reservoir.

In a second compression setting (e.g. “half-travel mode”), shown by path151 of FIG. 2, oil flow to the first IFP chamber 300 is blocked at valve200, causing all the pushed oil to flow into the second IFP chamber 400and therefore changing the effective spring rate of the system(increasing the spring rate by decreasing the available IFP gas volumebut therefore decreasing the available shock travel). The practicalresult of this half-travel setting is a stiffer-acting shock absorber.

A third compression setting includes the full closure of valve 200,effectively blocking oil flow to both IFP chambers 300, 400 andresulting in a shock absorber that is hydraulically locked out. Thethird setting is especially useful to prevent operation of the shockabsorber in conditions when its operation is unnecessary or unwanted bya user. The valve 200 may include a “blow off” or pressure relieffeature (optionally user adjustable) so that even when “locked out” theshock absorber may move in response to overpressure thereby avoidingdamage to the shock or vehicle or user.

In some embodiments, the three compression settings described areselectable via user-accessible controls mounted adjacent components ofthe shock absorber 100 or remotely (with appropriate signalcommunication to the shock absorber such as cable, wire, or wirelesswith servo motors). For example, in one embodiment, a knob is adjustablebetween three positions corresponding to the full-travel, half-traveland lock out modes/positions described herein. In addition to thecompression settings described, the shock absorber of the embodimentdescribed also permits adjustment of operation in a rebound stroke (e.g.adjustment of rebound damping). In the first and second settings, theIFP gas pressure in 302, 402 pushes fluid out of the IFP chambers 300,400 and back into the main cylinder fluid chamber 188 as the piston 180is moved in a rebound direction (shown as arrow 153). Each IFP has anexternally adjustable valve 303, 403 that allows the rebound flowingfluid to be metered, resulting in different rebound fluid flow speeds.In one embodiment, the rebound fluid is divided between the adjustablevalves and factory set shims (not shown). The valves 303, 403 permit auser to change the operational aspects of the IFPs for proper suspensiondepending on, among other things, road/trail conditions and loads. Ineach setting, both IFP cylinder oil chambers 301, 401 flow their reboundflow oil back to the main cylinder 178 through one common reboundadjustor valve and flow path. For example, in full-travel mode, allrebound fluid travels through and can be adjusted at valve 303 of IFP300. In half-travel mode, all fluid travels back towards the main damper125 via valve 403 of IFP 400.

Explaining the operation of some embodiments in more detail, themovement of oil flow out of the main cylinder oil chamber 188(compression flow shown as arrow 152) and oil back into the maincylinder oil chamber 188 (rebound flow 153) will be elaborated upon byexample. In the first compression setting (full-travel mode) and undercompression flow, oil will flow into the first IFP 300. Referring toFIG. 2 the full-travel mode flow path 150 comprises nodes 1-5 of FIG. 2.The IFP oil chambers 301, 401 will communicate with one another viafluid path 160 (nodes 4-5 including valve 322) connecting them. Thisfluid path includes valve 322 that allows flow to communicate in bothdirections between the IFP oil chambers 300, 400 when the shock is setin this first, full-travel compression setting. The compression dampingand the rebound damping in the full-travel compression setting will eachbe unique to this setting as the compression oil flow and rebound oilflow are directed into and out of only one of the IFP chambers (IFP 300via node 3) upstream of the fluid path 320 that permits both IFPchambers to communicate. A rebound adjustor valve 303 provided in path3-2 controls and adjusts the rebound flow for this full-travel setting.Shimmed or valved (shims being an example valve type) compression andshimmed or valved rebound damping (not shown) are also provided in path3-2 specifically for the full-travel setting.

When the shock is set to the half-travel setting, compression flow isdirected to second IFP 400 along path 151 as shown in FIG. 2. Note thatonly the gas IFP 400 is compressed because the IFP gas chambers areisolated from each other. Valve 322 in fluid path 160 is closed in thissetting in the direction of IFP 400 to 300. A low speed rebound adjustor403 is provided in path 151 to control low speed rebound damping forthis second compression setting condition, and distinct shimmedcompression damping (not shown) and rebound damping are provided in path151 specifically for this second, half-travel setting. Compression flowis now directed only into IFP 400 and rebound flow is supplied only fromIFP 400. While the operation is described utilizing the IFPs 300, 400 ina particular manner it will be understood that the chambers 300, 400could be reversed in function and sequencing.

The described embodiment provides half or full-travel operation and ineach case, the rebound flow of fluid moves in a single path and ismetered at a single location, thus avoiding a problem of prior artarrangements that leads one IFP crashing because it receives less fluidthan it expels due to unequal metering.

FIGS. 6-9 are section views showing portions of a suspension system thatinclude some of the embodiments described herein. FIGS. 6-7, for exampleillustrate the flow of fluid within the shock in full-travel modewhereby both of the IFPs 300, 400 are utilized in the operation. FIG. 8illustrates fluid flow in half-travel mode, wherein only one of the IFPs(400) is utilized.

FIG. 6 shows the path of fluid between the main damper 125 and valve200, which in the case of FIG. 6, is a spool valve (e.g. in oneembodiment a single valve member having multiple functions) with acentral shaft 205 for directing fluid in a variety of differentdirections depending upon the axial location of the shaft 205 relativeto the valve body and ports 220, 225 (FIG. 7) connecting the valve tothe IFPs 300, 400. In FIG. 6, a port 201 is visible for providing fluidcommunication between the main damper 125 and valve 200. In each FIG.6-9, fluid travel in a compression mode of the damper is shown by asolid line/arrow 230 while fluid travel in the rebound mode is shown bya dotted line/arrow 235. In FIG. 6, solid line 230 illustrates the pathof fluid during a compression stroke as fluid leaves the damper 125 andmoves into the valve 200 from which it will travel to both IFPs 300,400. FIG. 7 corresponds to FIG. 6 and shows fluid travel 230 from a port220 in the spool valve 200 directly to a first IFP 300. A separate path230 a is utilized to carry fluid from IFP 300 to IFP 400 through path160 which in the embodiment of FIG. 7, is included in spool valve 200.In the embodiment shown in the section views, valve 322, controllingfluid flow in flow path 320 (FIG. 2) is also incorporated into the spoolvalve 200 and the path of fluid through that path is determined by asetting of the valve.

Following the path of the dotted line 235, it will be appreciated that aportion of the fluid 235 a traveling out of (rebounding) IFP 300 can bemetered by rebound needle valve 303 (FIG. 2) that is adjustable by auser via adjustment knob 255 accessible at an upper end of the IFP 300.Another portion of the rebound fluid 235 is metered by shims (notshown).

FIG. 8 is a section view of the spool valve 200 and the IPOs 300, 400and illustrates the half-travel mode when only a single IFP 400 isutilized by the system. As shown in the Figure, fluid travel between thevalve and IFP 400 while IF 300 is not utilized. In the half-travel mode,only the gas spring portion of one IFP 400 is used and the systemtherefore operates with stiffer characteristics. Of note is the reboundpath of the fluid (dotted line 235) wherein a portion of the fluidtravels through another needle-type valve 403 (FIG. 2) that isadjustable via knob 256, thereby permitting the rebound characteristicsof the shock to be user-adjusted in the half-travel mode.

FIG. 9 is another section view showing both IFPs and the previouslydiscussed fluid path between them (valve C) having a one-waycharacteristic in which fluid may travel from IFP 300 to IFP 400 inhalf-travel mode of operation. The feature permits fluid in a non-usedIFP to move to the other IFP so it can be utilized in operation of theshock absorber.

The forgoing description and the Figures illustrate and teach a shockabsorber using one or more of multiple IFPs to provide differing andadjustable amounts of a spring function when the shock absorberoperates. In a dual IFP reservoir embodiment one mode provides that twoIFPs are used in a sequential manner whereby the fluid travels a pathbetween them from one to the next. In a rebound stroke of the shockabsorber the fluid travels back along the same or similar path, therebyproviding a single point of metering and avoiding some drawbacks ofearlier designs, most notably the possibility of an IFP locking up dueto expulsion of all of its fluid due to differing amounts of metering ofthe rebound fluid. In one embodiment the flow path between reservoirsincludes a one way flowing check valve disposed to check fluid flowentering the reservoir unused during half travel mode but allowing fluidto flow from that cylinder to the half travel damping reservoir. In thatway, any fluid trapped in the unselected cylinder while changing fromfull travel to half travel can freely flow back to the main cylinder, orotherwise into the selected damping circuit, as needed but no new fluidwill be introduced into the unselected reservoir during half traveloperation. It is noteworthy that several other flow options andcombinations are available in the shown embodiments.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A shock absorber comprising: a main damper cylinder having a variablevolume portion with a fluid therein; a first reservoir and a secondreservoir and a fluid flow path between the variable volume portion andat least one of the first and second reservoirs; and a second fluid flowpath between the first and second reservoirs.